In recent years, a portable communication device such as a portable telephone terminal has been provided with a circuit applicable to an RFID system in a high frequency (HF) band, and a communication terminal device has come into widespread use as a reader and writer or an RFID tag. However, with the reduction in the size and the increase in the function of a communication terminal, it is often difficult to provide a sufficient space for a coil antenna large enough to obtain a high gain, in a housing of such a communication terminal. In view of the foregoing, Patent Literature 1 (identified below) discloses a relay antenna to be arranged so as to extend in the upper direction of a portable telephone. This relay antenna is an auxiliary antenna for increasing a communication distance. In addition, Patent Literature 2 (identified below) discloses that a coil antenna is provided in a jacket to be attached to a portable communication device.
Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2006-048580.
Patent Literature 2: Japanese Patent No. 5660229.
Since a display panel or an operation portion are arranged in the front of a portable communication device, the above coil antenna is arranged on the rear face side of the device so as not to be affected by the display panel or the operation portion. In addition, in a case of communicating by holding a portable communication device over a reading portion of a communication partner device, such as a reader and writer, it is reasonable that a communication surface of the portable communication device is on the back side of a housing.
However, when an RFID tag is provided as a communication partner and an RFID tag-containing article containing the RFID tag are much smaller than a portable communication device, it is often difficult to align the portable communication device with the RFID tag-containing article, as will be described below. In other words, when an RFID tag-containing article is much smaller than a portable communication device, a user holds the portable communication device in one hand and holds the RFID tag-containing article in the other hand, and has to rub the RFID tag-containing article against the rear face of the portable communication device. In this scenario, since it is necessary to confirm whether or not communication has been established, the user has to perform an operation with the RFID tag-containing article hidden on the rear surface (surface on the opposite side of a display surface) of the portable communication device, while looking at the screen of the portable communication device.
FIG. 21 is a view of a state in which an RFID tag-containing article is hidden on the rear surface of a portable communication device. When a small-sized RFID tag-containing article 300 is brought close to a portable telephone terminal 200 from the side of a surface opposite to a display surface Sd of the portable telephone terminal 200, and a reading region (readable range) RA is small, the user has to move a position of the RFID tag-containing article 300 to find a position in which communication is possible until displayed content changes. In particular, a portable communication device with a small readable range needs time to establish communication.
In this manner, an inconvenience has arisen such that whether or not communication is established is not able to be determined unless the display of the screen is confirmed or such that, when positions have to be aligned, an operation has to be performed from a side on which the screen is not seen.
In addition, since the readable range of an RFID tag varies for each model of a portable communication device, an RFID tag-containing article has to be brought close by use of a mark that shows a reading position as a guide, the mark being attached to the back side of a device, and such an operation requires experience.
While, in the above examples, the portable communication device functioning as a reader and writer and an RFID tag communicate with each other, a similar inconvenience is also caused in a case in which a first device functioning as a reader and writer and a second device functioning as an RFID tag communicate with each other. Each of the first device and the second device conceptually includes, for example, a portable telephone terminal or a single RFID tag.